A mechanical component for an internal combustion engine including a mechanical component body that is made of aluminum or aluminum alloy, a manufacturing method of the mechanical component for the internal combustion engine, and a mechanical component including a mechanical component body that is made of aluminum or aluminum alloy are known, for example, as disclosed in JP08-158058A, which will be hereinafter referred to as Reference 1.
According to a mechanical component disclosed in Reference 1, an electroless nickel plating that includes phosphorus and boron is coated on a surface of a base material (i.e., a mechanical component body of the mechanical component) which is made of aluminum alloy, and then heat treatment is performed on the base material and the electroless nickel plating at a low temperature, for example, 200° C., so that a Vickers hardness of the electroless nickel plating is equalized to 800 HV or greater. In the mechanical component disclosed in Reference 1, because of the heat treatment at a low temperature, hardness of the electroless nickel plating is enhanced while hardness of the base material made of aluminum alloy is restrained from decreasing.
Nevertheless, in a case where the mechanical component disclosed in Reference 1 is placed under a high temperature environment, for example, at approximately 250° C. or more, hardness of aluminum alloy that constitutes the base material is reduced. Hardness difference between the electroless nickel plating of which hardness increases and the aluminum alloy of which hardness decreases becomes greater, which may result in easy peeling of the electroless nickel plating from the base material. Generally, in a case where the electroless nickel plating is coated on the surface of the base material made of aluminum alloy, a pre-process is performed. Specifically, the pre-process includes an etching process for causing the surface of the base material to be roughened so as to form an uneven surface, and a zinc immersion process for forming zinc plating which is replaceable with nickel. In the base material after the pre-process is conducted, a defect caused by corrosion at the surface, for example, may occur. Thus, in a case where the electroless nickel plating is peeled off from the base material, a crack may initiate at the aforementioned defect portion of the surface of the base material that is exposed because of the peeling of the electroless nickel plating. As a result, the mechanical component may be damaged from the portion at which the base material is exposed.
A need thus exists for a mechanical component for an internal combustion engine, a manufacturing method of the mechanical component for the internal combustion engine, and a mechanical component which are not susceptible to the drawback mentioned above.